Among various flat panel-type display devices having display screens of a few centimeters in thickness, liquid crystal display (LCD) devices are widely used in commercial applications. For example, they are employed for notebook computers, aircraft monitors and the like since they provide advantages such as low power consumption and portability.
An LCD device includes lower and upper substrates facing each other with a predetermined distance therebetween, and a liquid crystal layer formed between the lower and upper substrates.
The lower substrate includes gate and data lines crossing each other to define a unit pixel region. In addition, the lower substrate includes a thin film transistor TFT that functions as a switch and is formed adjacent to a crossing portion of the gate and data lines. Also, a pixel electrode is formed on the lower substrate and is electrically connected with the thin film transistor TFT.
The upper substrate includes a light-shielding layer, a color filter layer, and a common electrode. The light-shielding layer shields portions of the gate line, the data line and the thin film transistors except a pixel region from the light. Also, the color filter layer is formed on the pixel region, and the common electrode is formed on the upper substrate including the color filter layer and light-shielding layer.
The above LCD device includes various elements formed by a series of steps. For example, photolithography may be used to pattern the various elements.
Photolithography may increase the cost, time, and complexity of manufacturing an LCD device, since it requires a light-emission device, a mask having a predetermined pattern, and exposure and development steps.
To overcome these disadvantages of photolithography, a new patterning method that entails printing has been developed. In the printing method, a predetermined material is coated on a printing roller, and the printing roller is rotated on a substrate, thereby forming a predetermined pattern on the substrate.
FIGS. 1A to 1C are cross sectional views illustrating a printing method using a printing roller according to the related art.
As shown in FIG. 1A, first, a pattern material 30 is provided through a printing nozzle 10 and is coated on an outer surface of a printing roller 20.
Then, as shown in FIG. 1B, the printing roller 20 coated with the pattern material 30 is rotated (rolled) on a cliché plate 40 having concave and convex portions. That is, some pattern material 30b is transferred to the convex portions of the cliché plate 40, and the remaining pattern material 30a is left on the outer surface of the printing roller 20. As a result, a predetermined pattern 30a is formed on the printing roller 20 by the remaining pattern material 30a. 
As shown in FIG. 1C, as the printing roller 20 is rotated on a substrate 50, the predetermined pattern 30a of the printing roller 20 is transferred to the substrate 50.
The above method using the printing roller 20 utilizes the cliché plate 40 including the predetermined concave and convex portions. When some pattern material 30b of the printing roller 20 is transferred to the convex portions of the cliché plate 40 by rotation of the printing roller 20 on the cliché plate 40, it necessarily requires a cliché stage for fixing and supporting the cliché plate 40.
Also, as shown in FIG. 1B, after using the cliché plate 40 once, some pattern material 30b is left on the convex portions of the cliché plate 40. To reuse the cliché plate 40, a cleaning process is performed to remove the pattern material from the convex portions of the cliché plate 40.
FIGS. 2A and 2B are perspective and cross sectional views schematically showing the related art cliché stage.
In the related art cliché stage, as shown in FIG. 2A, a plurality of vacuum holes 60 for vacuum-suction and fixation of the cliché plate 40 are formed on the surface of the cliché stage 45.
Although not shown, the plurality of vacuum holes 60 are connected with a vacuum pump. Accordingly, when the cliché plate 40 is put on the cliché stage 45 having the plurality of vacuum holes 60, the cliché plate 40 is fixed on the cliché stage 45 by the vacuum force provided from the vacuum holes connected with the vacuum pump.
However, the related art cliché stage has the following disadvantages.
FIG. 3 is a cross sectional view showing a cleaning process of the cliché plate according to the related art.
As shown in FIG. 3, after the cliché plate 40 is provided on the cliché stage 45, the cliché plate 40 is fixed to the cliché stage 45 by the vacuum suction force. Then, the cliché plate 40 is cleaned.
To clean the cliché plate 40, a cleaner 70 sprays a cleaning solution 75 onto the cliché plate 40. The sprayed cleaning solution 75 may permeate into a space between the cliché plate 40 and the cliché stage 45, and thus may weaken the vacuum-suction force. Accordingly, it may be difficult to fix the cliché plate 40 in place in precise alignment with the cliché stage 45, and an imprecise pattern may be formed.
In addition, if the cleaning solution 75 permeates into the space between the cliché plate 40 and the cliché stage 45, the lower surface of the cliché plate 40 may be contaminated due to the cleaning solution 75.